The present invention relates to an apparatus for creating a seal in packaging material.
Apparatuses for creating seals in polymeric film are known in the art. In the past, these apparatuses have required products to undergo several mechanical steps for the product to ultimately become sealed in film. One past apparatus, U.S. Pat. No. 5,357,731, requires several sealing and cutting devices to seal a package. The package, as it moves along a conveyor, and is first sealed on the xe2x80x9cfrontxe2x80x9d end, sealed on the sides, then sealed on the xe2x80x9cbackxe2x80x9d end by three separate sealing wheels. After sealing, the film on the package is cut by a fourth cutting wheel.
A second apparatus, described in U.S. Pat. No. 5,237,800, similarly contains several sealing units, through which an article must pass to be sealed. The film on the article is first sealed by a center sealing unit, then the ends of the film are sealed by an end sealing unit and finally a heating unit to shrink wrap the film on the article.
In a third apparatus, described in U.S. Pat. No. 5,548,946, a package is sealed on the sides by sealing rollers and then the ends are sealed by cross seal tools which are attached to a casing. Another apparatus, U.S. Pat. No. 4,517,790, involves packaging film formed in a tube where an individual product is dropped into the tube. After passing through the tube an ultrasonic welder seals the front end of the packaging film and then the back end.
Because these apparatuses require the package to undergo several steps to be sealed, only a few packages may be sealed at a time. This results in a slower line speed decreasing overall productivity, and the required apparatus is excessively large and complex.
Other apparatuses, including that of U.S. Pat. No. 3,551,261, use sealing bars which move by means of pivot arms. In these type devices, the contact time of the blade on the film is controlled by a timing mechanism. When sealing the film, the bar is in the xe2x80x9cdownxe2x80x9d position and raised to the xe2x80x9cupxe2x80x9d position when sealing is complete. Only one product may be sealed at a time, and the up and down movement of the blade decreases the overall line speed of the products as they proceed through the sealing process.
Another apparatus, U.S. Pat. No. 5,603,801, uses a sealing blade controlled by a hydraulic air cylinder arm. The contact time of the blade with the film is controlled by a timing mechanism. As with the other apparatuses, this apparatus only permits one product to the sealed at a time, decreasing line speed of the products.
Other apparatuses use a servo-drive assembly for advancing a heat seal bar back and forth along a path to seal packages, for example, U.S. Pat. Nos. 5,755,923 and 5,968,306 which are incorporated herein by reference in their entirety.
The past apparatuses include complex, cumbersome structures involving various mechanisms to control the blade as it seals products. Accordingly, the complexity of these structures detract from the cost, reliability, and attainable line speed using these devices. It would be advantageous to develop an improved sealing apparatus that reliably seals packages at an increased line speed, and which would be relatively inexpensive to produce.
Accordingly, it is an object of the present invention to provide a sealing apparatus and method that enables products to be sealed at an increased line speed, allows for both ends of a package to be sealed in overlapping time periods by a retractable sealing device and is simple in design and inexpensive to produce.
It is an object of the present invention to provide a sealing apparatus that can seal packaging material at increased line speeds.
The foregoing and other advantages of the invention will become apparent from the following disclosure in which one or more preferred embodiments of the invention are described in detail and illustrated in the accompanying drawings. It is contemplated that variations in procedures, structural features and arrangement of parts may appear to a person skilled in the art without departing from the scope of or sacrificing any of the advantages of the invention.